PURPOSE OF REVIEW: Long-term oxygen treatment is one of the few interventions that improve survival in chronic obstructive pulmonary disease and it is widely used even though published evidence supporting the use of this treatment in chronic obstructive pulmonary disease is scanty. In addition, some studies do not demonstrate a mortality benefit for long-term oxygen treatment in this disease. It is important that long-term oxygen treatment be administered only to those patients who will benefit and in a manner that maximizes its efficacy. New studies are urgently needed to address these questions. RECENT FINDINGS: The published evidence for and against the use of long-term oxygen treatment in chronic obstructive pulmonary disease is summarized and problems with current guidelines and important areas for future research are discussed. SUMMARY: Future research will address the optimal timing and duration of oxygen therapy during rest, exercise and sleep, ways of identifying chronic obstructive pulmonary disease patients who are most likely to benefit and ways of improving patient compliance, all of which may have a profound effect on clinical practice. © 2007 Lippincott Williams & Wilkins.